Heat exchanger

ABSTRACT

A heat exchanger includes at least two adjacent heat exchanging tubes, each having equilateral triangular cross section. Hot gas flows through the heat exchanging tubes and coolant flows over the heat exchanging tubes. The heat exchanging tubes form a tube bundle of polygonal cross section and have two tube walls arranged in parallel side-by-side relation at a distance to one another.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2010 027 338.4, filed Jul. 15, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a heat exchanger.

It would be desirable and advantageous to provide an improved heat exchanger to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a heat exchanger includes at least two adjacent heat exchanging tubes, each having equilateral triangular cross section, with hot gas flowing through the heat exchanging tubes and coolant flowing over the heat exchanging tubes, wherein the heat exchanging tubes form a tube bundle of polygonal cross section and have two tube walls arranged in parallel side-by-side relation at a distance to one another.

As a result of the equilateral triangular cross section of the heat exchanging tubes, a heat exchanger according to the present invention exhibits a surface area which is about 1.3 times larger than in a conventional heat exchanger of circular cross section and same inner cross sectional area. The surface area of the heat exchanging tubes of a heat exchanger according to the present invention has maximum size and the heat exchanging tubes require considerably less installation space. Thus, a heat exchanger according to the present invention provides a comparably large heat exchanging surface between hot gas flowing in the heat exchanging tubes and the coolant sweeping over the heat exchanging tubes. While the surface area, compared to round tubes, is thus reduced by about a third, the cooling surface can be increased by about a third. The distance between the triangular heat exchanging tubes in the tube bundle can be varied to best utilize the cooling effect in accordance with the throughflow direction of the coolant. An example of coolant includes cooling water.

According to another advantageous feature of the present invention, the heat exchanging tubes can be made of steel.

According to another advantageous feature of the present invention, the heat exchanging tubes can be placed in such a way that the tube bundle exhibits a rhombic configuration. Such a disposition of the heat exchanging tubes results in an optimum relationship between the tube surfaces and the volume defined within the heat exchanging tubes. This manifests itself in particular when two, four, six, eight or more heat exchanging tubes of equilateral, triangular cross section are combined to form a rhombic tube bundle.

Coolant may flow transversely in relation to the heat exchanging tubes. Of course coolant may also flow longitudinally along the heat exchanging tubes in a same direction or in countercurrent direction.

According to another advantageous feature of the present invention, a shell having a rhombic cross section may be provided to ensheathe the heat exchanging tubes at a distance thereto. In this way, the space available for coolant can be utilized in an optimum manner. Advantageously, the shell can also be made of steel.

According to another advantageous feature of the present invention, the shell may have inclined walls, with bypass tubes extending laterally adjacent to the inclined walls. The bypass tubes, like the heat exchanging tubes, may have an equilateral cross section. As an alternative, the bypass tubes may have a round cross section.

According to another advantageous feature of the present invention, a housing having a rectangular cross section may be provided to ensheathe the tube bundle and the bypass tubes. Advantageously, the housing can be made of steel sheet.

According to another advantageous feature of the present invention, the heat exchanging tubes may also be placed in such a way that the tube bundle exhibits a hexagonal configuration. As a result, the shell may thus also be configured of hexagonal cross section to ensheathe the heat exchanging tubes at a distance thereto.

According to another advantageous feature of the present invention, the heat exchanging tubes may be provided with protuberances and/or grooves. In this way, heat transfer can be optimized. The protuberances and/or grooves may have a round, half-round, rhomboid, triangular, or oval configuration. The protuberances and/or grooves may extend in longitudinal direction of the heat exchanging tubes or also have a helical configuration.

According to another advantageous feature of the present invention, a turbulence generator can be inserted in the heat exchanging tubes. This further enhances heat transfer.

According to another advantageous feature of the present invention, a tube sheet may be provided to couple the heat exchanging tubes to form the tube bundle. Currently preferred is a configuration of the tube sheet in the form of a baffle plate or optionally in the form of a sheet metal water deflector.

According to another advantageous feature of the present invention, a heat exchanger according to the present invention may form part of an exhaust gas recirculation system for an internal combustion engine, wherein the hot gas is exhaust gas of the internal combustion engine and the coolant is cooling water. In other words, part of exhaust gas is recirculated in a cooled state back to the combustion chamber of the internal combustion engine. Recirculation of cooled exhaust gas results in an increased proportion of inert gas in the air mixture. As a result of the lesser oxygen concentration in the mixture, combustion progresses more controlled and at lower combustion temperatures which reduce development of NO_(x) in the combustion chamber.

In view of the optimal triangular heat exchanging tubes in the exhaust gas recirculation system, efficiency of the cooler can be significantly increased while the installation space is the same and the back pressure is reduced at the same time.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 is a schematic cross section of a basic principle of a heat exchanger with two heat exchanging tubes;

FIG. 2 is a schematic cross section of another embodiment of a heat exchanger;

FIG. 3 is a schematic cross section of the heat exchanger of FIG. 2 with provision of additional bypass tubes;

FIG. 4 is a schematic cross section of a modification of the heat exchanger of FIG. 3 with provision of an ensheathing housing;

FIG. 5 is a schematic cross section of yet another embodiment of a heat exchanger;

FIG. 6 is a schematic cross section of the heat exchanger of FIG. 5 with provision of additional bypass tubes;

FIG. 7 is a schematic cross section of the heat exchanger of FIG. 6 with provision of an ensheathing housing;

FIG. 8 is a schematic illustration of a heat exchanging tube with grooves;

FIG. 9 is a schematic illustration of a heat exchanging tube with inserted turbulence generator;

FIG. 10 is a schematic illustration of heat exchanging tubes connected by a tube sheet;

FIG. 11 is a schematic illustration of heat exchanging tubes connected by a sheet metal water deflector; and

FIG. 12 is a schematic illustration of a heat exchanging tube with protuberances.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is shown a schematic cross section of a basic principle of a heat exchanger, generally designated by reference numeral 1 and including two heat exchanging tubes 2 which are made for example of steel and arranged side-by-side. Hot gas HG flows through the heat exchanging tubes 2 and coolant KF flows outside the heat exchanging tubes 2. The heat exchanger 1 forms part of a not shown exhaust gas recirculation system for an internal combustion engine, also not shown. Thus, the hot gases HG involve hot exhaust from the internal combustion engine for flow through the heat exchanging tubes 2, whereas the coolant KF is cooling water flowing over the heat exchanging tubes 2.

The heat exchanging tubes 2 have an equilateral triangular cross section and are combined to form a tube bundle RB of rhombic cross section, with two neighboring tube walls 3, 4 of the heat exchanging tubes 2 extending side-by-side in parallel relation. A cartridge or shell 5 made of steel for example and having a rhombic cross section ensheathes the heat exchanging tubes 2 about their circumference. FIG. 1 shows the presence of distances A of same size between the heat exchanging tubes 2 as well as between the heat exchanging tubes 2 and walls 6 of the shell 5.

FIG. 2 shows a schematic cross section of another embodiment of a heat exchanger, generally designated by reference numeral 1 a and including a total of eight heat exchanging tubes 2 having equilateral triangular cross section and combined to form tube bundle RB of rhombic configuration. Of course, bundling of more or less than eight heat exchanging tubes 2 to form tube bundle RB is conceivable as well. The disposition of the heat exchanging tubes 2 in relation to one another and in relation to the peripheral shell 5 corresponds to those shown in FIG. 1 so that a further discussion is not necessary.

FIG. 3 shows a schematic cross section of the heat exchanger 1 a, with addition of bypass tubes 7, 7 a being provided adjacent to the heat exchanger 1 a next to inclined walls 8 of the shell 5. The bypass tubes 7, 7 a are positioned in parallel relation to the heat exchanging tubes 2 in proximity of wails 9 of the shell 5, which extend horizontally in the drawing plane. The bypass tubes 7, 7 a may have equilateral triangular cross section and/or round cross section. By way of example, bypass tubes 7 have equilateral triangular cross section and bypass tubes 7 a have round cross section.

FIG. 4 shows a schematic cross section of a modification of the heat exchanger 1 a, and it can be seen that the shell 5 of rhombic cross section which ensheathes the heat exchanging tubes 2 and the bypass tubes 7, 7 a, is in turn surrounded by a housing 10 having rectangular cross section and being made of steel for example.

FIG. 5 shows a schematic cross section of yet another embodiment of a heat exchanger, generally designated by reference numeral 1 b. In the following description, parts corresponding with those in FIG. 1 will be identified, where appropriate for the understanding of the invention, by corresponding reference numerals followed by a “b”. The description below will center on the differences between the embodiments. In this embodiment, the heat exchanger 1 b includes a total of six heat exchanging tubes 2 which have equilateral triangular cross section and are combined to form a hexagonal tube bundle RB1. The tube bundle RB1 is ensheathed by a shell 5 b of hexagonal configuration. The disposition of the heat exchanging tubes 2 relative to one another and the disposition of the heat exchanging tubes 2 relative to the peripheral shell 5 b correspond to those in the embodiment of FIG. 1 so that a further discussion is not necessary.

FIG. 6 shows a schematic cross section of the heat exchanger 1 b, with addition of bypass tubes 7, 7 a being provided adjacent to the heat exchanger 1 b of hexagonal configuration next to inclined walls 11 of the shell 5 b which ensheathes the heat exchanging tubes 2 of equilateral triangular cross section. The bypass tubes 7, 7 a again may have equilateral triangular cross section and/or round cross section. By way of example, bypass tubes 7 have equilateral triangular cross section and bypass tubes 7 a have round cross section.

FIG. 7 shows a schematic cross section of a modification of the heat exchanger 1 b, and it can be seen that the shell 5 b of hexagonal cross section which ensheathes the heat exchanging tubes 2 and the bypass tubes 7, 7 a, is in turn surrounded by a housing 10 b having rhombic cross section.

The heat exchanging tubes 2 may be provided with grooves 12 and/or protuberances 16, as shown by way of example in FIGS. 8 and 12. The grooves 12 or protuberances 16 may have a round, half-round, rhomboid, triangular, or oval configuration and extend in longitudinal direction of the heat exchanging tubes. To enhance heat transfer, the heat exchanging tubes 2 can have inserted therein a turbulence generator 13, as shown in FIG. 9.

As shown in FIG. 10, a tube sheet 14 may be provided to couple heat exchanging tubes 2 to form the tube bundle RB, RB1. The tube sheet 14 can be configured in the form of a baffle plate or in the form of a sheet metal water deflector 15, as shown in FIG. 11 by way of example.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 

1. A heat exchanger, comprising at least two adjacent heat exchanging tubes, each having equilateral triangular cross section, with hot gas flowing through the heat exchanging tubes and coolant flowing over the heat exchanging tubes, said heat exchanging tubes forming a tube bundle of polygonal cross section and having two tube walls arranged in parallel side-by-side relation at a distance to one another.
 2. The heat exchanger of claim 1, wherein the heat exchanging tubes are made of steel.
 3. The heat exchanger of claim 1, wherein the coolant is cooling water.
 4. The heat exchanger of claim 1, further comprising a shell having a rhombic cross section and ensheathing the heat exchanging tubes at a distance thereto.
 5. The heat exchanger of claim 4, wherein the shell is made of steel.
 6. The heat exchanger of claim 4, wherein the shell has inclined walls, and further comprising bypass tubes extending laterally adjacent to the inclined wails.
 7. The heat exchanger of claim 6, further comprising a housing having a rectangular cross section and ensheathing the tube bundle and the bypass tubes.
 8. The heat exchanger of claim 7, wherein the housing is made of steel sheet.
 9. The heat exchanger of claim 1, further comprising a shell having a hexagonal cross section and ensheathing the heat exchanging tubes at a distance thereto.
 10. The heat exchanger of claim 9, wherein the shell is made of steel.
 11. The heat exchanger of claim 9, wherein the shell has inclined walls, and further comprising bypass tubes extending laterally adjacent to the inclined walls.
 12. The heat exchanger of claim 11, further comprising a housing having a rhombic cross section and ensheathing the tube bundle and the bypass tubes.
 13. The heat exchanger of claim 12, wherein the housing is made of steel sheet.
 14. The heat exchanger of claim 1, wherein the heat exchanging tubes are provided with protuberances and/or grooves.
 15. The heat exchanger of claim 14, wherein the protuberances and/or grooves have a round, half-round, rhomboid, triangular, or oval configuration.
 16. The heat exchanger of claim 14, wherein the protuberances and/or grooves extend in longitudinal direction of the heat exchanging tubes or have a helical configuration.
 17. The heat exchanger of claim 1, further comprising a turbulence generator inserted in the heat exchanging tubes.
 18. The heat exchanger of claim 1, further comprising a tube sheet to combine the heat exchanging tubes to form the tube bundle.
 19. The heat exchanger of claim 18, wherein the tube sheet is constructed as a sheet metal water deflector.
 20. The heat exchanger of claim 1, forming part of an exhaust gas recirculation system for an internal combustion engine, wherein the hot gas is exhaust gas of the internal combustion engine and the coolant is cooling water. 